Independent efficacy trials indicate that a selective eating disorder prevention program involving dissonance- inducing activities that decrease thin-ideal internalization in high-risk female high school and college students with body dissatisfaction reduces eating disorder risk factors, eating disorder symptoms, and risk for onset of future eating disorders and obesity relative to alternative interventions and assessment-only control conditions, with some effects persisting through 3-year follow-up. A large effectiveness trial found that this intervention reduced risk factors and eating disorder symptoms relative to a psychoeducational brochure control condition through 2-year follow-up when high school counselors and nurses recruited participants and delivered the intervention. Yet the effects from this latter trial were slightly smaller than those in the efficacy trial, potentially due to limited infrastructure, funds, and staff to support prevention programs in high schools. It is thus possible that this intervention will produce larger effects in an effectiveness trial involving colleges, as they typically have staff devoted to mental health programming with group intervention training and access to appropriate facilities. Although we conducted our initial effectiveness trial with high school students, there have been no effectiveness trials of empirically supported eating disorder prevention programs for college students; this is an important lacuna because the environment, resources, and endogenous providers are very different for colleges versus high schools and because there are over 1 million US female college students with threshold or subthreshold eating disorders. A large effectiveness trial involving multiple regions with a diverse sample would also permit an investigation of facilitator and participant factors that predict intervention effect size. We propose to conduct a 3-site effectiveness trial that tests whether this prevention program produces effects when college counselors, psychologists, and nurses recruit, screen, and deliver the intervention under ecologically valid conditions. We will randomize 432 high-risk young women with body dissatisfaction recruited from 9 colleges in Oregon, Pennsylvania, and Texas to the dissonance program or a psychoeducational brochure control condition. We will use an enhanced facilitator training procedure and newly published facilitator manuals and participant workbooks. Participants will complete a survey and a diagnostic interview at pretest, posttest, and 1- and 2-year follow-ups. We will test whether (1) the dissonance program results in larger reductions in risk factors, eating disorder symptoms, risk for future eating disorder and obesity onset, functional impairment, and mental health treatment relative to controls, (2) intervention effects are mediated by change in thin-ideal internalization, (3) certain factors moderate program effects (e.g., initial body dissatisfaction level), (4) process factors (e.g., intervention fidelity) predict larger effect sizes, (5) the savings produced by this intervention offset intervention delivery costs, and (6) colleges continue to offer the prevention program after they complete the 1-year intervention-delivery phase of this trial (i.e., assess sustainability). PUBLIC HEALTH RELEVANCE: Threshold and subthreshold eating disorders affect over 10% of adolescent girls and are associated with functional impairment, distress, medical complications, risk for obesity onset, and the highest mortality of any psychiatric condition; accordingly, a pressing public healthy priority is to develop effective prevention programs for eating pathology. The proposed project will be the first effectiveness trial to test whether an eating disorder prevention program with strong empirical support from efficacy trials produces effects under ecologically valid conditions among high-risk female college students, which is a vital step toward widespread dissemination of programs developed with NIH funding. The proposed cost-effectiveness analyses and examination of process factors that predict larger intervention effects will also represent novel contributions to the literature.